The aim of this proposal is to study hydrogen ion secretion using clearance, micropuncture, and microperfusion techniques. The mechanism(s) whereby chronic renal failure enhances bicarbonate reabsorption will be studied. We will also determine whether or not an adaptive increase in hydrogen ion secretion occurs following acute reduction in the renal mass. Renal hydrogen ion handling will be studied in rats with aldosterone deficiency in order to clarify the mechanism of metabolic acidosis of this condition. The role of phosphate depletion and excess parathyroid hormone in determining the metabolic acidosis of hyperparathyroidism will be evaluated. The renal acidification defect caused by glucose and insulin administration, amphotericin, lithium chloride administration will be studied by clearance and micropuncture techniques. The factors controlling hydrogen ion secretion in the proximal tubule, distal tubule and collecting duct will be evaluated under normal conditions and in the presence of induced acidification defects. The mechanisms whereby alkalinization of the urine increases urinary pCO2 will be studied by micropuncture. The interrelationship of potassium and hydrogen ion secretion will be studied.